As Schlanger steps out the front door of a house she is staying in during a fellowship, she notes the smell of the plants in the air. She wonders if this smell indicates that they are communicating with one another. In addition to “intelligence” and “consciousness,” the word “communication” is controversial among botanists. The term implies intent: To communicate is to share knowledge with purpose. However, Schlanger points out that communication is the key to all cellular development: “For life to open to the possibility of multicellularity, individual cells had to coordinate among themselves” (55). Even a single seed contains an embryonic root with a cluster of cells communicating about the exterior conditions and the right moment to emerge.

The debate about whether plants communicate traces back to a 1979 paper published in Plant Resistance to Insects by zoologist David Rhoades-Davey, who was interested in a caterpillar population that had been feeding on trees at the University of Washington campus. One year, the caterpillars abruptly started to die. Rhoades’s research revealed that the trees had changed their chemistry, sickening and killing the caterpillars. Even more surprisingly, Rhoades discovered that faraway trees, ones nowhere near where the caterpillar infestation, also changed their chemical composition.